1). Field of the Invention
This invention relates to an electronic package of the type having a microelectronic die and to a method of constructing an electronic package.
2). Discussion of Related Art
Integrated circuits are usually manufactured in and on semiconductor wafer substrates that are subsequently “singulated” or “diced” into individual microelectronic dies, each die carrying a respective integrated circuit. Such a die may be extremely thin, often less than 100 microns, and is subsequently mounted to a package substrate for purposes of structural integrity. The package substrate also has conductors in the form of traces thereon, metal lines therein, and/or vias therein to provide electric interconnection to other devices, often other integrated circuits or other dies mounted to the same package substrate.
In order to save space in x and y, it is often required to stack more than one die on top of one another in a z-direction, with integrated circuits of the dies interconnected with one another. Two dies can, for example, be mounted to a flexible substrate, and the flexible substrate be folded into positions such that the dies are above one another.
A package substrate of the aforementioned kind is usually uniformly flexible across its width. When one portion of the package substrate is folded over another portion of the package substrate, a fold region may be created at an undesired, even arbitrary area of the package substrate. Folding of the substrate at undesired areas may cause damage to certain components of the substrate. Bending at arbitrary locations may cause inconsistencies in bending from one assembly to the next, which may result in incorrect downstream packaging. Uncontrolled folding may also result in an undesired formfactor of the final electronic package.
FIGS. 4A–D illustrate one manner of forming an existing electronic package. In FIG. 4A, two microelectronic dies 310 are mounted via two other microelectronic dies 312 to a flexible package substrate 314. A cover piece 316 is located over the microelectronic dies 310, the microelectronic dies 312, and the flexible substrate 314. The cover piece 316 has a protrusion 318 contacting a fold portion 320 of the flexible substrate 314.
As illustrated in FIG. 4B, mold caps 324 are subsequently injection-molded within remaining spaces defined within the confines of the cover piece 316, microelectronic dies 310, microelectronic dies 312, and flexible substrate 314. When the cover piece 316 is removed, as illustrated in FIG. 4C, it can be seen that the mold caps 324 form square edges 326 facing one another, with the fold portion 320 between the edges 326.
As illustrated in FIG. 4D, the fold portion 320 is subsequently folded to place a portion of the flexible substrate 314 carrying one of the microelectronic dies 310 over a portion of the flexible substrate carrying the other microelectronic die 310. Folding of the fold portion 320 is not controlled, and is not consistent from one package to the next.